Relative positions of optical counterpart centres respect nominal PSZ1 coordinates for clusters in Table A.1 flagged as “1” (crosses), “2” (squares), and “3” (triangles). Only optical counterparts with multiple detections are excluded. The inner dashed line show the region (of 2.′ 8 radius) enclosing 68% of the confirmed clusters (flagged as “1” and “2”). The external dashed line corresponds to 2.5 times the beam size (5′) of Planck SZ detections.